Expansible mandrel for sinking or driving pipes into the ground



Oct. 31, 1961 A. P. JOURDAIN 3,006,151

EXPANSIBLE MANDREL FOR SINKING 0R DRIVING PIPES INTO THE GROUND Filed May 17, 1957 2 Sheets-Sheet 1 Oct. 31, 1961 Filed May 17, 1957 A. P. JOURDAIN EXPANSIBLE MANDREL F SINKING OR DRIVING PIPES INTO E GROUND 2 Sheets-Sheet 2 United States Patent 3,006,151 EXPANSIBLE MANDREL FUR SKNKENG OR DRHVING PIPE INTO THE GROUND Andre Paul Jonrdain, Embourg-lez-Liege, Belgium, as-

signor to Compagnie Internationale dcs Pieux Armes Frankignoul, Saciete Anonyme, Liege, Belgium Filed May 17, B57, Ser. No. 659,930 Claims priority, application France May 22, 1956 5 Claims. (Cl. til-53.72)

The invention relates to an expansible mandrel intended for sinking or driving hollow pipes into the ground by a driving force applied to the upper end of the mandrel, the said pipes then being filled with concrete or the like for forming foundation posts. The invention is concerned more especially with a mandrel of the type comprising a certain number of radially movable longitudinal sectors, which are adapted to be forced against the internal face of the pipe to be sunk and which are arranged around a central part or core, inflatable tubes made of rubber or the like being provided for causing the expansion of the mandrel by the inflation of the tubes, thereby displacing the sectors radially outwards in relation to the core, so as to force them against the wall of the pipe. Furthermore, means are provided for displacing the sectors radially toward the core when the said tubes are deflated, so as to bring the mandrel into the contracted position, which enables it to be introduced into the pipe to be sunk or to be raised after the sinking or driving operation. In one known mandrel of this type, each sector is provided with a longitudinal vane of hook form which, in conjunction with a corresponding hookshaped blade or flange, forms two chambers succeeding one another radially, one of which serves as a housing for an inflatable expansion tube and the other as a housing for an elastic return member which can be formed by an inflatable tube or 'a non-inflatable elastic tube.

The invention has as an object the provision of an expansible mandrel controlled by inflatable tubes, the construction, mounting, dismantling and cleaning of which are very simple and in which practically the entire internal surface of the sectors is free, so as to enable a greater number of inflatable tubes to act on said mandrel, this permitting the expansion force to be considerably increased, thereby facilitating the sinking of smooth pipes, although it is usual to employpipes having a corrugated wall, ribs formed on the external surface of the sectors being adapted to engage in the said corrugations.

To this end, the invention provides for the core to occupy the major part of the mandrel cross-section so as only to leave, between the core and the sector assembly in the position of expansion of the mandrel, an annular space having a Width smaller than the normal diameter of the inflatable tubes, i.e. when they are of circular cross-section, the inflatable tubes bearing directly on the external surface of the core and on the internal surface of the sectors, while the radial guiding action of each sector relatively to the core is insured by a central rib provided on one of these elements and sliding in a corresponding guideway provided on the other of these elements.

It is expedient that the inflatable tubes, for example made of rubber or the like, should in practice not be dilatable so that the length of their periphery remains practically constant.

Longitudinal ribs may be provided on the core and/or on the sectors for defining housing for the individual tubes.

When the pressure in. the expansion tubes is relieved,

the sectors are freed from any force and, especially if a 3,096,151 Patented Oct. 31, 1961 vacuum is created in these tubes, it may be possible to extract the contracted mandrel so that it can then be used for driving in a fresh tube. It is however expedient to provide a forced return of the sectors against the core as soon as the pressure is relieved in the inflatable tubes, so that the mandrel remains positively closed during the operations of introduction into and extraction from the pipe. To this end, the invention provides rubber or like spring working under compression, which are each interposed between two elements, one of which is connected to the core and the other to the sector, so as to be compressed during the expansion movement of the mandrel. These rubber blocks are preferably prestressed when the mandrel is assembled, so that they are already compressed to a certain degree in the contracted position of the mandrel.

Other features and advantages of the invention will be apparent from the description of one embodiment, which is hereinafter given by reference to the accompanying drawings wherein:

FIG. 1 is a longitudinal section on line 1-1 of FIG. 2, showing a mandrel according to the invention, in its expanded position,

FIG. 2 is a sectional view on enlarged scale, taken'on line II-II of FIG. 1,

' Fig. 3 is a partly sectional View on enlarged scale, taken on line III-III of FIG. 1,

FIG. 4 is a view on enlarged of FIG. 1,

FIG. 5 is a fragmentary axial section of a modification in the expanded position of the mandrel,

FIG. 6 is a corresponding view in transverse section, and

FIG. 7 is a view corresponding to FIG. 6, but in the contracted position of the mandrel.

The mandrel comprises a plurality of independent radially movable longitudinal sectors 1, these being for example three in number, the curvature thereof being adapted to that of the pipe 2 which is to be sunk, this pipe being corrugated in the example illustrated, although it could be smooth. At its upper end, each sector is connected to a head 4 by any suitable connection permitting the sectors to move radially with respect to the head, this connection being for example obtained by means of bolts 5, which are not tightened so as to permit this relative movement. The head is adapted to receive the hammering forces and to transmit these forces tothe expansible mandrel.

In the case of FIGS. 1 to tubular sections 6 connected by blocks forming the upper end which is in contact with the head 4, and also the lower end. Although this is not essential, the core can be fixed at its bottom end to an enlarged base 8. The bottom end of each sector then rests on this enlarged base.

Expansible tubes 9 are arranged between the sectors and the core. The bottom end of each tube is closed, while the upper end thereof is connected to a source of compressed air and possibly to a source of vacuum, by means of flexible pipes 10, it being possible for the connection to the said source to be made by any suitable means.

The core is formed with the housings for the tubes 9,

scale, showing a detail 3, the core is formed by solid blocks 7, two similar longitudinal ribs 11 defining one rib being more especially opposite the center line of each sector. These central ribs are interrupted at the level of the blocks 7, where the ribs 12 are provide on the sectors in the same planes as the ribs 11. These ribs 12 are engaged in grooves 13 formed in the blocks 7 so as to insure radial guiding of the sectors. At least some of these ribs 11 and 12 can serve as stop abutments when the mandrel is contracted.

It will be understood that "as a result of this construction, all the annular space between the core and the sectors is available in practice for fitting the inflatable tubes 9 therein, a larger number of which can then be provided than in the known constructions, this permitting a greater expansion force to be developed.

Each sector is formed at the height of one or more of the blocks 7 with a bolt 14 which extends through the corresponding rib 12 and block 7 and which carries, at its end remote from the sector, a washer 15 which bears on a. rubber or like block 16 forming a return spring and mounted in a recess 17 of the block 7. The nut 13 enables prestressing to be set up, that is to say, precompression of the spring 16.

Similar rubber or like springs 19, 20 can be provided at the ends of each sector, it being possible for these springs to be fitted in a prestressed condition, for example, with the aid of means such as those illustrated in FIG. 4. The spring 20 is arranged in a mounting formed in the base 8. Before the mandrel is assembled, the block 20 is compressed by means of a screw 21, the end of which is screwed into an angle iron 22, the nut 23 permitting the required compression to be set up. After assembly, a lug 24 integral with the corresponding sec tor l is positioned behind the said angle iron. The screw 21 is then removed.

As the expansion travel of the sectors is small, these rubber springs working with compression are much more efiicien-t than the conventional springs working with tension. Moreover, they are practically indestructible, since they are not subject to rust and are insensitive to shocks. Furthermore, they take up very little space and do not apply a load to the members in which they are encased.

in order to facilitate the contraction of the mandrel when the pressure in the tubes 9 is relieved, the invention provides for these sectors being suspended with slight play from the head 4 by means of bolts 5, which are each arranged on or inside the vertical line passing through the centre of gravity of the corresponding sector, so that after the pressure in the tubes 9 has been relieved, the bottom end of each sector does not have a tendency to be displaced outwardly, but rather inwardly. This arrangement facilitates the contraction of the mandrel.

In the example illustrated, the mandrel is designed for sinking pipes comprising successive sections ofincreasing diameters, so as to be able to benefit from the advantages inherent in the use of this type of pipes, particularly the use of sinking machines with a smaller height, since thesmaller diameter section of a fresh pipe which is to be sun-k can be provisionally engaged in a pipe which is already sunk, this facilitating the positioning of the mandrel in the pipe which is to be driven in. Each sector comprises a part of smaller diameter which extends over the full height of the mandrel, while on the upper section of larger diameter, a supplementary casing is fixed to the outside of the sector.

in the case of a corrugated pipe 2, the sectors are provided with external ribs 25, for example helical ribs, which penetrate into the corrugations. In order to insure that the sectors of the mandrel are suitably disengaged from the pipe corrugations 2 with a contracting movement which is as small as possible, the invention provides for the radius of curvature of the ribs 25 to be equal to or somewhat smaller than that of the external surface of the sectors.

FIGS. to 7 show a construction which permits the use of a continuous pipe 26 as the core, and this may have advantages from the point of view of simplicity of the construction and of possibilities of application, since there is then available a continuous central space over the entire height of the mandrel. The rubber springs can then be arranged in the annular space between the core and the sectors without a bolt extending though the core. Such an arrangement comprises for example a U-sh-aped member 27 welded to the tube 26 and serving as a housing for the rubber block 28. The bolt 29 acts on the block 28 by means of a washer 30, while the nut 31 bedded in the sector 1 enables the rubber to be prestressed. An axial recess 32 in the U-shaped member 27 permits easy mounting. Although the sectors are already guided by this assembly, it is possible to provide ribs 33 welded to the inside of the sectors for improving this guiding action by co-operating with the U-shaped members 27.

As the nuts 18 and 31 are accessible from outside, it will be understood that the adjustment of the prestressing of the rubber springs can easily be effected and that dismantling of the sectors is simple.

It is obvious that the invention is not limited to the construction described and illustrated and that various modifications may be incorporated therein without departing from the spirit of the invention.

What I claim is:

1. An expansible mandrel for positioning pipes in the ground, said mandrel comprising a plurality of radially movable longitudinal sectors cooperatively defining a predetermined cross-section, a central core of smaller dimension than said cross-section and arranged within said sectors and extending longitudinally thereof, said sectors defining a free space with the core, first radial guide means .on said core, second radial guide means on each of the sectors and each cooperating with the first guide means for guiding the sectors in radial direction with respect to the core, said first and second guide means being located substantially in common planes extending outwardly from the center of said cross-section, elastic return means between each of the sectors and the core and tending to move the sectors towards the core in order to contract the mandrel, said return means being positioned substantially in said planes and being spaced from each other along the longitudinal extent of the core, at least two inflatable tubes associated with each sector and extending longitudinally thereof in said free space on both sides of said guide and return means, and means [for connecting the inflatable tubes to a source of pressure medium to inflate said tubes for displacing the sectors radially outwards with respect to the core, the central core comprising tubular sections and intermediary sections having a substantially thicker wall than said tubular sections connecting the tubular sections, said second radial guide means being ribs fixed to the sectors and said first guide means being guideways provided in the intermediary sections.

2. An expansible mandrel for positioning pipes in the ground, said mandrel comprising a plurality of radially movable longitudinal sectors cooperatively defining a predetermined cross-section, a central core of smaller dimension than said cross-section and arranged within said sectors and extending longitudinally thereof, said sectors defining a free space with the core, first radial guide means on said core, second radial guide means on each of the sectors and each cooperating with the first guide means for guiding the sectors in radial direction with respect to the core, said first and second guide means being located substantially in common planes extending outwardly from the center of said cross-section, elastic return means between each of the sectors and the core and tending to move the sectors towards the core in order to contract the mandrel, said return means being positioned substantially in said planes and being spaced from each other along the longitudinal extent of the core, at least two inflatable tubes associated with each sector and extending longitudinally thereof in said free space on both sides of said guide and return means, and means for connecting the inflatable tubes to a source of pressure medium to inflate said tubes for displacing the sectors radially outwards with respect to the core, the return means comprisin rubber blocks interposed between the core and the sectors so as to be compressed during the expansion of the mandrel, and means for placing the rubber blocks under adjustable initial stress.

3. An expansible mandrel as claimed in claim 2, wherein each rubber block is mounted in a crecess provided in the core, said mandrel comprising, for each block, a bolt which extends diametrally through the core, block, and associated sector, and a nut bearing against the latter said sector and engaging the said bolt for retaining the block in position.

4. An expansible mandrel for positioning pipes in the ground, said mandrel comprising a plurality of radially movable longitudinal sectors cooperatively defining a predetermined cross-section, a central core of smaller dimension than said cross-section and arranged within said sectors and extending longitudinally thereof, said sectors defining a free space with the core, first radial guide means on said core, second radial guide means on each of the sectors and each cooperating with the first guide means for guiding the sectors in radial direction with respect to the core, said first and second guide means being located substantially in common planes extending outwardly from the center of said cross-section, elastic return means between each of the sectors and the core and tending to move the sectors towards the core in order to contract the mandrel, said return means being posi tioned substantially in said planes and being spaced from each other along the longitudinal extent of the core, at least two inflatable tubes associated with each sector and extending longitudinally thereof in said free space on both sides of said guide and return means, and means for connecting the inflatable tubes to a source of pressure medium to inflate said tubes for displacing the sectors radially outwards with respect to the core, said core being a continuous tube and each return means including a rubber block and two radially aligned pressure members sandwiching the block and connected to the core and to a sector respectively.

5. An expansible mandrel as claimed in claim 4, wherein one of said pressure members is a U-shaped member fixed to the core and defining therewith a space for accommodating one of said rubber blocks, the other pressure member including a plate, a bolt on the plate and extending through the associated rubber block, said one pressure member and he corresponding sector, and a nut on the bolt and bearing against the said corresponding sector.

References Cited in the file of this patent UNITED STATES PATENTS 1,872,688 Dealy Aug. 23, 1932 2,027,800 Whitlock Jan. 14, 1936 2,170,188 Cobi Aug. 22, 1939 2,321,146 Jones June 8, 1943 2,334,386 Cortella Nov. 16, 1943 2,424,635 Schwall July 29, 1947 2,437,043 Riemenschneider Mar. 2, 1948 2,625,015 Cobi Jan. 13, 1953 2,684,577 Smith July 27, 1954 2,741,093 Riker Apr. 10, 1956 2,871,666 Pickman Feb. 3,, 1959 FOREIGN PATENTS 1,096,444 France 1955 755,498 Great Britain Aug. 22, 1956 84,885 Netherlands Apr. 15, 1957 

